This invention relates to an electric circuit interrupter of the vacuum type and, more particularly, to a circuit interrupter of this type which comprises two sets of relatively movable contacts electrically connected in parallel for carrying continuous current through the interrupter.
In most vacuum interrupters, the force required to hold a pair of separable contacts in engagement during the passage of high current therethrough varies directly with the square of the current. It has been recognized that this force can be reduced by providing a plurality of sets of contacts electrically connected in parallel for sharing the total current through the interrupter. One way of constructing such an interrupter is to mount the movable contact of each pair on the usual long, slender movable contact rod and to arrange these movable contact rods in close side-by-side relationship. A problem involved in such an arrangement is that the high magnetic forces developed between the movable contact rods when high currents flow therethrough tend to force the rods together, making it difficult to properly guide and operate the contact rods. One way of dealing with this problem is disclosed and claimed in our copending application Ser. No. 546,475, filed Feb. 3, 1975, and assigned to the assignee of the present invention. This applicaton has now issued as U.S. Pat. No. 3,969,598.
A general object of our invention is to construct a vacuum type circuit interrupter comprising parallel-connected pairs of contacts in such a way as to reduce the transversely-directed magnetic forces acting on the movable contact rods during high currents as compared to those transversely-acting forces usually present in prior side-by-side contact rod arrangements such as referred to above.
Another object is to construct a vacuum-type circuit interrupter comprising parallel-connected contacts in such a way that the contacts can be accommodated within an envelope of relatively small diameter as compared to that needed when the contact pairs are disposed in side-by-side relationship.
One embodiment of our invention employs interleaving rod electrodes, such as shown and claimed in U.S. Pat. No. 3,679,474-Rich, assigned to the assignee of the present invention, for carrying the arcing current after arcing has been initiated at the separable contacts.
Another object is to combine the parallel-connected contacts of the interrupter with these rod electrodes in such a way that the interrupter effects a prompt transfer of arcing current from the inner-contact gaps to the gaps between the rod electrodes.